In addition to imaging the night sky and studying astrophysics, I am actively engaged in a number of research projects.
1. Determination of period changes in SX Phoenicis variable stars
SX Phe stars are low metallicity stars located within the instability strip of the Hertzsprung-Russell diagram. They are a type of variable star, with short pulsations usually no more than a few hours in length.
The star DY Pegasi was observed between 2006 and 2012 using the 60cm classical Cassegrain reflector at the York University Astronomical Observatory. Data was collected through a Johnson I-band filter using an SBIG ST-9 CCD.
By observing DY Peg, alongside comparison and check stars, I reduce and analyze this data by performing differential photometry on the variable star in IRAF. By fitting a polynomial to the resulting light curve, the time of maximum light for each cycle is calculated and recorded as a Heliocentric Julian Date (HJD).
Current models allow for the calculation of the star's pulsation period. By matching observed maxima to these calculated maxima, a nonzero rate of change of pulsation period can be found. My goal is to measure this rate of change.
Typical research image of DY Peg and check/comparison stars
Polynomial fit of DY Peg light curve
The nature of this change provides key insight into the astrophysical processes occurring within these types of variable stars. By measuring these period changes, it is then possible to refine our current understanding of the processes that occur within a star that is leaving the main sequence, and beginning the end phases of its life.
2. Multispectral analysis of the Type Ia supernova SN 2014J
Type Ia supernovae occur when a white dwarf star has accreted enough matter from a companion in its system to ignite nuclear fusion. The energy released through fusion exceeds the binding energy of the star, and the white dwarf explodes.
There is a small range of masses below the Chandrasekhar limit of 1.4 solar masses in which a given white dwarf will explode; as a result, the release of energy is remarkably consistent across all Type Ia supernovae. The corollary of this is that there is a standard to which any Type Ia measurement can be compared.
SN 2014J occurred in the galaxy M82, and was discovered on 21 January 2014. Using the 40cm Schmidt-Cassegrain reflector at the York University Astronomical Observatory, multispectral images were obtained between 23 January and 27 February 2014 through Johnson B, V, R, and I-band filters using an SBIG ST-9 CCD.
Existing photometric techniques produce poor results for embedded objects, especially as measured from heavily light polluted environments. Using the technique of PSF fitting to remove the galactic influence, and using a well established Type Ia supernova model provided by Nugent, Kim, & Perlmutter (2002), it was possible to vastly reduce the deleterious effects of the local and extragalactic environments on the supernova data quality, producing an accurate light curve that agrees with current literature on this event.
Typical R-band research image of SN 2014J and check/comparison stars
Multispectral light curves of SN 2014J before reduction techniques
Multispectral light curves of SN 2014J after reduction techniques
Early analysis of this data has shown a distance to SN2014J of 4 ± 1 Mpc, a time of max light (MJD in the B-band) of 56690.3 ± 0.5, and an extinction parameter of Rv = 3.4 ± 0.6. These values are encouraging, and suggest further refinement of analysis techniques will produce more precise results; these results may allow for an in-depth analysis of the extinction effects observed, and an investigation into the consistency of reddening laws between our galaxy and M82.
Analysis of reddening and extinction will allow for a greater understanding of the effect of cosmic dust on observed astronomical light, which in turn allows for a more precise understanding of the nature of cosmic dust. Additionally, we do not expect that reddening laws will vary significantly across similar galaxies; any determination of the consistency of these laws will provide insight into the nature of galactic chemical evolution.
I presented these reduction techniques at the 2015 Canadian Undergraduate Physics Conference, in Peterbourough, Ontario.
3. Measuring the abundance ratio [Ar III]/[S III] in metal-rich nebulae
HII regions and planetary nebulae are large 'clouds' in space. The former is a region in which star formation is, or has recently, taken place; the latter is the remnant of a low-mass star after its death. As stars die and spread their elements around the galaxy, the chemical composition of these nebulae change over time; the 'newest' of these nebulae are rich in metals produced throughout the history of the host galaxy.
A number of HII regions in M81 were observed by C. Stevenson, M. McCall, and R. Kennicutt between 25-27 January 1992. Data was acquired with a 90-inch Cassegrain telescope at the Kitt Peak Observatory, using a CCD and a Boller/Chivens Spectrograph. I am reducing this data for further analysis in which the spectral line strengths of [AR III] and [S III] are to be extracted.
Following a 1992 paper 'Ar/S' by Stevenson, McCall, and Welch, these observations are being used to verify the proposition that the relative line strengths of [AR III] to [S III] can be used as an indirect method of temperature measurement in metal-rich nebulae.
On the assumption that this ratio is a universal constant arising from the nature of Ar/S formation, this ratio may prove a reliable indicator for measuring nebulae temperatures below ~10,000K.
If this method is demonstrated to be accurate, it will allow for the measurement of nebulae temperatures to greater precision at low temperatures, and provide a valuable check for existing models of nebula dynamics. By refining such models, a better understanding of galactic chemical evolution may be achieved.
4. Investigating the role of star formation in producing AMEs
In the 1990s, it was discovered that there was an anomalous microwave emission (AME) peaking around 30GHz that appeared to be associated with thermal emission from interstellar dust. However, the anomalous emission didn't appear to be consistent with free-free emission from this dust. An alternate explanation was put forth that this emission was actually electric dipole rotational emission from very small dust grains under normal interstellar conditions. The theoretical basis of this explanation was so sound that this has become the accepted explanation for the emission.
Nonetheless, certain regions in the sky appear to have particularly strong 30GHz emission. Collaborating with a Research Fellow at the European Space Agency, we investigated the role that star formation may have in producing this spinning dust emission. Star formation occurs in very dusty regions of the galaxy, and young stars produce intense radiation that permeates the surrounding dust environment. The radiation pressure would be strong enough to produce a torque on small dust grains, kicking a large number of them into a rotational mode capable of producing this electric dipole rotational emission. Therefore we would expect to see active 30GHz regions have some correlation with areas of star formation. To investigate this, we made us of data from the Planck and WISE satellites.
Spinning dust emission, distinct from thermal emission and free-free emission.
Colour-colour diagram showing part of the selection process for finding YSOs.
We identified 28.2 million distinct point sources matching our search criteria for potential new stars. We adopted a classification scheme for identifying Young Stellar Objects (YSOs) from these point sources (Koenig et. al., 2012), rejecting 15.8 million sources star-forming galaxies, AGNs, shock emission objects, and resolved or unresolved PAH candidates. 12.3 million sources were rejected as post-YSO stars, and 96,871 YSOs were identified as Class I or Class II. We limited this number to those which fell within a one degree radius of any of the 98 regions centred on AMEs detected by Planck.
No correlation could be found between the number of YSOs in these regions, and any of the measurements of these regions by Planck. There are two possible reasons. The first is that star formation has no impact on producing spinning dust emission.
However, it is worth noting that in such an intense radiation and dust environment, YSOs would likely have some effect on the Planck parameters measured, even if it is insignificant; no such effect was detected.
This suggests the second possibility, which is that the resolution difference between WISE and Planck is too great to detect the role of star formation in these AME regions. The Planck data at 30GHz has a resolution many times worse than the WISE data between 3.2 and 12 microns. Therefore, while it was possible to resolve the positions of the YSOs spatially in WISE, it was impossible to spatially correlate the AME emissions and YSO positions. It could be that the AME emission measured in a 1 degree radius is concentrated around the YSO areas; only higher resolution 30GHz imagery would allow for that determination.